docs: add release-notes

Author: ziggie1984

docs/release-notes/release-notes-0.21.0.md

@@ -54,8 +54,10 @@
     refacotor the payment related LND code to make it more modular.
   * Implement the SQL backend for the [payments 
     database](https://github.com/lightningnetwork/lnd/pull/9147)
-  * Implement QueryPayments for the [payments db 
+  * Implement query methods for the [payments db 
     SQL Backend](https://github.com/lightningnetwork/lnd/pull/10287)
+  * Implement insert methods for the [payments db 
+    SQL Backend](https://github.com/lightningnetwork/lnd/pull/10291)
 
 ## Code Health